14 Jun
2006
14 Jun
'06
6:03 p.m.
On Saturday 10 June 2006 06:03 pm, Tony Duell wrote:
I think the single valve was a thyratron (gas-filled triode) used much as
you suggest.
Somewhere I have the issue of Practical
Television magazine which gives
construction details for a 1 valve + CRT scope. OK, there are some
semiconductor rectifiiers in the PSU too. The valve is for the timebase,
the Y input goes straight to the CRT plates. But it was useable for the
signals in vavle TVs of the time, and a lot better than nothing.
Bet you could do the timebase without a valve, too -- I was looking seriously
at a circuit that used a couple of neon bulbs as a triggered devices in a
relaxation oscillator some years back...
What did they use for a CRT? I have a 3" one in storage that as I recall
wants something like 1000V for an accelerating potential, and a transformer
to develop that isn't exactly trivial.
I think it used a normal valve HT transformer (which would give, perhaps,
700V between the ends of the secondary winding), with a voltage doubler
circuit.
-tony